In Plato’s Republic, the author describes a mythical token called the Ring of Gyges that confers upon its wearer the power of invisibility. Plato asks, would someone wearing the ring steal from a market or enter his neighbour’s house, knowing he would never be caught and punished, or would he refrain from bad behaviour and follow an innate code that tells us it’s always wrong to steal and invade others’ privacy?

‘We are now able to test Plato’s ideas in real life,’ Edward Lucas writes in his new book, Cyberphobia, comparing the ring’s gift of invisibility to the near-anonymity conferred on anyone using the internet, ‘and the results are depressing for those who believe that morality is instinctive. Under the cloak of anonymity which the internet bestows, people feel they can be rude,